Eukaryotic and Prokaryotic Cells

Cells in Biology

• All cells share common features enabling their function
• Eukaryotic and prokaryotic cells are the two main categories in biology

Eukaryotic Cells

• Animal and plant cells are eukaryotic
• Eukaryotic cells possess essential components like a cell membrane, cytoplasm, and ribosomes
• The genetic material (DNA) in eukaryotes is enclosed within a nucleus
• Eukaryotic cell size ranges from 10 to 100 μm

Prokaryotic Cells

• Bacteria exemplify prokaryotic cells
• Genetic material exists as a single DNA loop within the cytoplasm instead of a nucleus
• Plasmids, with smaller circular DNA, may be present in prokaryotes
• A cell wall made of peptidoglycan surrounds prokaryotic cell membranes
• Prokaryotic cells are smaller than eukaryotic, often measuring ~1 µm

Scale and Size

• Micrometers (µm) are the units used to measure cell size
• 1 µm equals 0.001 mm, 1x10-3 mm, and 1x10-6 m
• Conversion between mm and µm can be achieved by multiplying or dividing by 1000
• Eukaryotic subcellular structures can be of similar size to prokaryotic cells

Standard Form

• Handling subcellular sizes requires using standard form
• To convert, use the formula: 1. 5 µm ÷ 1000 = 0.0015 mm, which converts to 1. 5 x 10-3

Animal Cells

• Eukaryotic, with subcellular structures performing specific functions
• Organelles are compartments where specific processes occur

Key animal cell structures:

• Nucleus
• Cell membranes
• Mitochondria
• Ribosomes
• Cytoplasm
• Electron microscopes reveal some cellular structures

Plant Cells

• Possess same subcellular components as animal cells
• Cellulose cell wall is a key feature (also in algal cells)
• A permanent vacuole containing cell sap is present
• Chloroplasts are found in leaf and stem cells

Plant Cell Structures

• Cell Wall: Made of cellulose polymer, offering support and shape
• Chloroplasts: Contain chlorophyll pigments to absorb light for photosynthesis
• Permanent Vacuole: Fluid-filled for storing materials; provides cell support

Cell Specialization

• Specialized cells adapt their structure to perform specific functions
• Differentiation is the process of cell specialization

Specialized Animal Cells

• Nerve cells (neurons): facilitate information transit from brain and spinal cord
• Electrical impulse conduction is their main function

Specialized Features:

• Elongated shape enables connection across body areas
• Cytoplasm extensions (dendrites) enable communication with various cells
• Fatty sheath-covered axon speeds up impulse transmission
• Muscle cells contract due to layers of fibers

Muscle Cell Features:

• Movement from contraction
• Many mitochondria for energy release
• Protein filaments that slide for contraction
• Sperm cells are mobile reproductive cells possessing a tail
• Genetic transfer to egg cell is their purpose

Sperm Cell Design:

• Mitochondria-packed mid-piece fuels tail movement
• Tail rotation achieves propulsion
• Acrosome in head releases digestive enzymes to penetrate egg
• Nucleus carries half the standard chromosome count

Specialized Plant Cells

• Root hair cells facilitate absorption in the soil
• Absorption of water and minerals is the function

Root Hair Features:

• Increased surface area from root hairs optimizes osmosis
• Thin walls aid water by shortening diffusion
• Mitochondria promote mineral's active transport
• Xylem vessels conduct water/ions using continuous tubes
• Water transport is their purpose

Vessel Adaptations:

• Lacking walls creates uninterrupted tubes for water flow
• Absent organelles enable unimpeded flow
• Lignin-stiffened walls offer reinforcement
• Phloem cells transport dissolved amino acids and sugars
• Transport of dissolved substances is their function

Pholem Adaptations:

• End-to-end cell joining with perforated walls enable continuous passage
• Sparse subcellular structures facilitate transport

Cell Differentiation

• Varying cell structures enable certain tasks within organisms
• Cell differentiation leads to specialized cells
• Undifferentiated cells can become specialized

Multicellular Traits:

• Specialized cells have varied gene usage to control growth
• Differentiated cells gain structure supporting their roles
• Nerve cell formation requires cytoplasm to enable distant connections
• Animal cells typically specialize early with cell division restricted to maintenance
• Plants retain differentiation ability

Microscopy

• Enhanced view of subcellular structures with gradual advancements
• 17th century: Light microscopes using lenses for magnified viewing
• 20th century: Electron microscopes use electron beams for higher resolution

Electron Microscopy

• Higher resolving power for increased magnification
• Enables finer study of cells and organelles like mitochondria
• Improves understanding of nucleus and cell membrane

Magnification Calculations

• Formula is: Magnification = Image size ÷ Actual size
• An equation triangle can assist in rearranging the formula

Converting Units in Biology

• Ensure uniform units when calculating magnification
• Convert to the same unit before calculating magnification

Light Microscope Use

• Aims to observe, draw, and label cells, including scale of magnification
• Biological drawing production and specimen observation are key for creating scaled drawings

Preparing a Microscope Slide

• Prepare specimens carefully to avoid harm
• Typical specimens: onion and cheek cells
• Stains accentuate cell structures (methylene blue for cheek, iodine for onion)

Using a Microscope

• Grasp microscope by the arm
• Begin with lowest power objective lens

Biological Drawings

• Represent what the microscope eyepiece reveals
• Drawings should be proportional, sharp, clear and scientifically accurate
• Labelling with straight, uncrossed lines is essential
• Aim for biological drawings that are as large as possible

Culturing Microorganisms

• Binary fission is a bacteria's method of reproduction
• Cell prepares, replicates genetic material, increasing is size for the fission
• Each DNA piece migrates before cytoplasm splits and the walls arise
• Two cells are formed from one

Growing Bacteria

• Allows study of antibiotic interaction
• In approximately 20 minutes, bacteria such as coli double in optimal conditions
• Nutrients and favorable warmth, up to 25°C promote growth, but inhibits the growth of harmful pathogens

Keeping Cultures Uncontaminated

• Preventing environment interference is essential
• Aseptic methods are vital
• Petri dishes and culture medium should be high temperature, to kill any potential microorganisms
• Always pass inoculating loop through a flame
• Petri Dishes should be left untouched as much as possible
• Secure dishes
• Don't incubate > 25°C

Inhibition Zone Area

• Helps calculates the effects of disinfectants, antibiotics and antiseptics
• (πr^2) to compute the area
• Make sure you take several diameter measurements and then average the results

Bacteria in Population

• Population changes can be analyzed
• Determining how many cell have been produced requires identifying a cells average division time

Standard Form

• In standard form, you would right it 131072. = 1.31072 + 2 x 10
• The power of 10 is the number to places the first decimal place moves

Microbiology Practical

• Studying antiseptics/antibiotics with area measurements on certain agar plates
• Perform aseptic techniques
• Calculating area of particular zones
• Ensure the species examined is not affected
• Control group needed (sterile water)